The invention relates to a sewing machine, and more particularly relates to a needle dropping hole changing control device of a sewing machine. The U.S. Pat. No. 4,303,028 discloses a needle dropping hole changing device, in which a pulse motor is employed for changing the needle position as well as the needle dropping hole from the laterally elongated one to the reduced circular one and vice versa, in dependence upon the stitching type such as the straight stitching or zigzag stitching which requires swinging movement of the needle. According to this prior art, the pulse motor changes the needle position and the needle dropping hole at the same time while the sewing machine is standstill. The pulse motor is, therefore, required to have a considerably powerful drive force. Accordingly the pulse motor is too large for the limited space of the machine housing. Moreover the increased inertia of the pulse motor produces an adverse influence to the swinging response of the needle.
It is therefore a general object of the present invention to eliminate such defects and disadvantages of the prior art. According to the invention, although the pulse motor changes the needle position in dependence upon the stitching type, it is required to function only for setting a control device which is operated by the starting drive of the sewing machine to change the needle dropping hole. The pulse motor is, therefore, not directly connected to the drive transmission linkage to the needle plate, but connected thereto through the intermediate control device, so that the load to the pulse motor may be remarkably reduced.
Thus it is a primary object of the invention to provide a control device between the stitch control pulse motor and the drive transmission linkage to the needle plate, so as to reduce the load applied to the pulse motor.
It is another object of the invention to operate the control device by the starting drive of the sewing machine to change the needle dropping hole in dependence upon the stitching type.